Check Engine Light - 2000 Yukon

[funkill]

Hi all!

My light came on late last week and I stopped at AutoZone to have them pull the code. This is what they found:

OEM code: P0440

Definition
EVAP (evaporative emission system) small leak/no flow condition

Explanation
The evaporative emission system is monitored for it's ability to hold vacuum.

Probably cause
1. Defective or loose fuel cap
2. EVAP canister or hose cracked - not connected
3. Purge or vent solenoid defective
4. Vacuum leak at engine

Of course, I checked the fuel cap and don't see a problem there - light remains ON. And I don't hear any obvious vacuum/sucking sounds.

I am suppose to leave for my first camping trip in 9 months in a couple days - to Eagle Lake in CA - about 280 miles round trip. I am busy de-winterizing and packing my bearings (hope the inner bearings go without hitch - first time doing these ones).

Would you drive and/or tow with this condition? Thanks for your thoughts on this!

Laura

[Cracker]

There's a remote possibility that it's under warranty. Many emission-related items have an extended warranty period - maybe even for a 2000 era Yukon. It wouldn't hurt to check with a GMC dealer. No need to have them pull the code - just give them what you have and let them tell you if its under warranty. Good luck!

[JDS]

I had a similar issue with my '04 Suburan. It's Ok to drive/tow but you'll want to have it fixed as it can affect the engine control computer and possibly reduce power/increase gas mileage. Mine wasn't covered by any warranty.

John S.

[Okotoks]

Doubtful its under warranty unless there is a recall accompanying the code. Manufacture extended emission warranties are usually no longer than 7 years and then only covered if your state has emission testing and your vehicle fails and the failure is caused by whatever is setting the code.
the small evap code is probably caused by a cracked rubber hose somewhere beteween the tank, canister, purge solenoid and or engine. I would not worry about traveling with that code set, depending on the size of the evap leak and location you may smell fuel vapors especially when it's hot which is not different to any vehicle with out evaporative emissions system.

[alclad]

Airstream, Inc :: Home

[Airslide]

I would agree that its ok to drive or tow. The fault is in the diagnostic side of the evap controls and is most likely posting this fault because the pressure sensor is reading that the system cannot hold a small amount of vacuum or pressure to test the fuel tank that makes sure the gas cap is on tight etc.. You will have to get it repaired to pass the smog check but otherwise it wont affect the running. If you smell fuel speed that process up though.. :-)

Vinnie

[Bruce B]

It is pretty unlikely it is under warranty after 12 years.
As to driving with the check engine light on as long as the light is not blinking (indicative of a misfire) you are probably ok. You should never drive a car with a blinking check engine light as you are risking catalytic converter failure if you do. I do this for a living and if it were my car I'd take it in for a diagnosis before I left. It might be a faulty gas cap, it could be a vacuum leak (usually detected with a smoke machine), it could be a faulty evap control valve and I have even seen damage from mice chewing through plastic lines. I always feel better when I know the actual cause of the issue and then I can decide if the issue can wait or not. Take it in to a good mechanic if for no other reason than the peace of mind that comes from knowing that everything is ok (at least for the moment). The other reason I'd personally want that light out (problem repaired) is that in case something else happens you will know as the light will turn back on....There is no way to know if the light is already illuminated for a previous issue.
Bruce

[Airline]

Why risk it ?
It needs to be fixed anyways.
If its a vacuum leak,you want to get it fixed asap.
Take it to a Chevy/GMC dealer since they work on these every day.

[funkill]

Thanks for the quick reply. I don't know if I can actually get to a mechanic before the trip. Right now it's either go or not - if not, then I can get to the mechanic....

I'll let you know what I decide. I live out in BFE and the closest mechanic is too far to work into the schedule... and by living in BFE (high desert), I have lots of mice who have done their dirty work on other hoses... Ahhhhhhhhhhh

Laura

now to post my next question in another area (re: bearing grease).

[Jammer]

Laura

Most often this code is caused by cracks in the O-ring seal on the gas cap. With ethanol in the fuel they don't last forever and if it hasn't been replaced yet it's probably time. You can buy a new gas cap at any auto parts place for a few dollars. I put a little grease on the o-ring for new ones so they seal a little better and are easier to remove.

[drunkensloth]

Just so you know, even if the fuel cap was loose and you tightened it, the light will not go off immediately. The system needs to run and pass a self test that will only run during a cold start and only if certain perameters are met. If I was in your position, I would replace the fuel cap with an OEM cap, clear the code(disconnect the battery if necessary) and then drive it. Worst case, the light will come back on. The evap issue won't affect your trip, but as Bruce said, if another fault occurs when the light is on, you won't know. Its very common for the ratchet mechanism in the cap to fail and not fully tighten.

[richinny]

on some vehicles you can trip that code by refueling with the engine running.

[DKB_SATX]

Originally Posted by drunkensloth

Just so you know, even if the fuel cap was loose and you tightened it, the light will not go off immediately. The system needs to run and pass a self test that will only run during a cold start and only if certain perameters are met. If I was in your position, I would replace the fuel cap with an OEM cap, clear the code(disconnect the battery if necessary) and then drive it. Worst case, the light will come back on. The evap issue won't affect your trip, but as Bruce said, if another fault occurs when the light is on, you won't know. Its very common for the ratchet mechanism in the cap to fail and not fully tighten.

I'll second this. Most of the minor codes that light the CEL cause it to stay on for some predefined time period (a number of starts, etc.) This is to establish a level of sensitivity to transient events, so that if you have a problem that happens once or twice per day, it'll keep the CEL lit until you correct the problem, but if you have something that occurs every 6 months or so, you'll have a CEL for a day or two and it'll go away for months, potentially driving you crazy in the process.

[funkill]

So, today the CEL is off! I don't know if it was due to meeting the particular number of starts before clearing or that my battery was low. I left the cargo door ajar and it wouldn't start but there was enough power to light the dome and maintain the clock time. Drove it to town - @40 miles RT - and the CEL did not relight!!!

Thanks for your help. I'll monitor the CEL.

Laura

[Splitrock]

I had the same issue. I tightened the gas cap to many clicks, then I removed the negative battery cable and let it sit that way over night. Next morning I reattached the cable. That reset the computer. No more warning code.

[AlbertF]

Originally Posted by funkill

Would you drive and/or tow with this condition? Thanks for your thoughts on this!

Laura

Yes, I have for years! My tow vehicle has a chronic P0400 code condition. It doesn't affect ecoconmy, reliability or drivability, so I've never bothered to deal with it.


Ironically, if I clear the code it never reappears while towing, only in warm weather solo.

[funkill]

Soooooooooo - the CEL continues to come on, then go off intermittently. I will be in town this afternoon and will pick up a new gas cap to see if that resolves the problem once and for all. I Googled the problem and found one post that said *dusty roadways* could affect the P0400 code. Hummmm, I certainly have that condition - dusty is almost an understatement. For now, I won't freak about the condition. But will need another smog test in a few months and I'll investigate further if the light is still illuminated!

Laura

[perryg114]

My Ranger had a cracked fill hose on the gas tank thanks to ethanol in the gas. You might want to check that. If you smell gas look for the source. I would not worry about that particular code. You can reset code with the code reader instead of resetting the whole computer. There is usually a training period everytime you reset the computer. It fine tunes the engine and transmission for the best performance. If you keep resetting it, it will constantly be in a tuning mode and may not drive as well as usual.

Perry

[funkill]

Fixed! I stopped to purchase a new gas cap and, upon closer inspection of my original, I realized it was filled with dust. Couple blasts of air to blow out the crud and now the CEL is OFF!

Laura